Neurology Physiology

• Neuroectoderm:
• -CNS neurons
• -ependymal cells
• -oligodendroglia
• -astrocytes

• Neural Crest Cells:
• -PNS neurons
• -Schwann cells

• Mesoderm:
• -Microglia

"Microglia like Macrophages originate from Mesoderm"

-signal-transmitting cells of nervous system

-permanent cells (don't divide in adulthood, no progenitor stem cell population)

• Dendrites: receive input (stain with Nissl: RER)
• Axons: send output (no RER)

• -injured axons
• -degeneration distal
• -axonal retraction proximal
• -allow for potential regeneration if in PNS

• Function:
• -physical support, repair
• -K+ metabolism
• -removal of excess NT
• -maintenance of BBB
• -reactive gliosis in response to injury

Marker = GFAP

• Function:
• -CNS Phagocytes (mesoderm)
• -NOT visible in Nissl stain
• -respond to tissue damage by differentiating into large phagocytic cells

• Appearance:
• -small irregular nuclei
• -relatively little cytoplasm

**HIV-infected microglia fuse to form multinucleated giant cells in CNS

• Function:
• -wraps and insulates axons
• -increases conduction velocity and space constant
• -saltatory conduction btwn nodes of ranvier

• Made by:
• -CNS: oligodendrocytes
• -PNS: Schwann cells

• Function:
• -myelinates multiple CNS axons (up to 50)
• -predominant glial cell in white matter

• Appearance:
• (on Nissl stain)
• -small nuclei with dark chromatin and little cytoplasm
• -fried egg on H&E

**destroyed in Multiple Sclerosis

• Function:
• -myelinates 1 PNS axon
• -promotes axonal regeneration
• -derived from neural crest
• -increased conduction velocity

**destroyed in Guillain Barre

Acoustic Neuroma: schwannoma of CNVIII

• 1. Free nerve endings
• 2. Meissner's corpuscles
• 3. Pacinian corpuscles
• 4. Merkel's discs

• C: slow, unmyelinated fibers
• A delta: fast, myelinated fibers

• Location:
• -all skin, epidermis
• -some viscera

• Senses:
• -pain and temperature

• Large, myelinated fibers
• **adapt quickly

• Location:
• -glabrous (hairless) skin

• Senses:
• -dynamic fine/light touch
• -position sense

Large, myelinated fibers

• Location:
• -deep skin layers
• -ligaments
• -joints

• Senses:
• -pressure
• -vibration

• Large, myelinated fibers
• **adapt slowly

• Location:
• -Hair follicles

• Senses:
• -pressure
• -deep static touch (shapes, edges)
• -position sense

-single nerve fiber layers ("inner")

**Inflammatory infiltrate in Guillain Barre

-surrounds a fascicle of nerve fibers ("around")

**must be rejoined in microsurgery for limb attachment

"Perineurium = Permeability barrier"

• -dense connective tissue
• -surrounds entire nerve ("outer")

**surrounds fascicle and blood vessels

• 1. NE
• 2. DA
• 3. 5-HT
• 4. ACh
• 5. GABA

• Synthesis:
• -Locus ceruleus (pons) ("stress and panic")

• INCREASED IN:
• -anxiety

• DECREASED IN:
• -depression

• Synthesis:
• -Ventral Tegmentum
• -Subthalamic Nucleus (midbrain)

• INCREASED IN:
• -schizophrenia

• DECREASED IN:-Parkinson's
• -Depression

• Synthesis:
• -Raphe nucleus (pons)

• DECREASED IN:
• -anxiety
• -depression

• Synthesis:
• -Basal nucleus of Meynert (pons)

• INCREASED IN:
• -REM sleep

• DECREASED IN:
• -Alzheimer's
• -Huntington's

• Synthesis:
• -Nucleus accumbens (reward center, pleasure, addiction, fear)

• DECREASED IN:
• -Anxiety
• -Huntington's

• Formed by:
• 1. Tight junctions between nonfenestrated capillary endothelial cells
• 2. Basement membrane
• 3. Astrocyte foot processes

• Functions:
• -helps prevent bacterial infections
• -restricts drug delivery to brain

• Glucose and AAs:
• -cross slowly by carrier-mediated transport

• Nonpolar/lipid soluble substances:
• -cross rapidly by diffusion

• Areas with no BBB:
• -fenestrated capillaries and no BBB
• -OVLT: osmotic sensing
• -Area postrema: vomiting after chemo
• -Neurohypophysis: ADH release

Infection/Neoplasm destroy tight junctions --> vasogenic edema

Hypothalamic inputs and outputs permeate the BBB

• "The hypothalamus wears TAN HATS"
• Thirst and water balance
• Adenohypophysis control
• Neurohypophysis (releases hormones)
• Hunger
• Autonomic regulation
• Temperature regulation
• Sexual urges

• Inputs:
• -OVLT (osmolarity changes)
• -area postrema (response to emetics)

• Supraoptic nucleus makes ADH
• Paraventricular nucleus makes oxytocin

ADH and oxytocin are made in the hypothalamus but stored and released by posterior pituitary

• 1. Lateral area
• 2. Ventromedial area
• 3. Anterior hypothalamus
• 4. Posterior hypothalams
• 5. Suprachiasmatic nucleus

HUNGER

• -destruction leads to anorexia/failure to thrive (infants)
• -inhibited by leptin

"If you zap your lateral nucleus you shrink laterally"

SATIETY

-destruction (ie: by craniopharyngioma) leads to hyperphagia

"If you zap your ventromedial nucleus you grow ventrally and medially"

• COOLING
• -pArasympathetic

"A/C = anterior cooling"

• HEATING
• -Sympathetic

"If you zap your posterior hypothalamus, you become a piokilotherm (cold-blooded like a snake)"

CIRCADIAN RHYTHM

"You need sleep to be charasmatic"

• Receives hypothalamic projections
• -supraoptic nucleus (ADH)
• -paraventricular nucleus (oxytocin)

Neurohypophysis

• -major relay for all ascending sensory information except olfaction

• VPL
• VPM
• LGN
• MGN
• VL

• Input:
• -Spinothalamic tracts
• -Dorsal Columns/Medial lemniscus

• Info:
• -Pain and Temperature
• -Pressure, Touch, Vibration, Proprioception

• Destination:
• -primary somatosensory cortex

• Input:
• -Trigeminal
• -Gustatory

• Info:
• -face sensation
• -taste

• Destination:
• -primary somatosensory cortex

"Makeup goes on the face (VPM)"

• Input:
• -CNII

• Info:
• -Vision

• Destination:
• -Calcarine Sulcus

"Lateral - Light"

• Input:
• -Superior olive and inferior colliculus of tectum

• Info:
• -Hearing

• Destination:
• -Auditory cortex of temporal lobe

"Medial = Music"

• Input:
• -basal ganglia

• Info:
• -Motor

• Destination:
• -Motor Cortex

• Functions:
• Emotion
• Long term memory
• Olfaction
• Behavior Modification
• ANS system function

• Structures:
• -hippocampus
• -amygdala
• -fornix
• -mamillary bodies
• -cingulate gyrus

• "the famous 5Fs"
• Feeding
• Fleeing
• Fighting
• Feeling
• Fornicating

• Functions:
• -modulates movement
• -aids in coordination and balance

• Input:
• -contralateral cortex via MCP
• -Ipsilateral proprioceptive info via ICP from spinal cord (input nerves = climbing and mossy fibers")

• Output:
• -Purkinje neurons --> deep nuclei of cerebellum --> SCP --> contralateral cortex

• Deep Nuclei:
• "Don't Eat Greasy Foods" (lateral to medial)
• Dentate
• Emboliform
• Globose
• Fastigial

• Functions:
• -voluntary movements and making postural adjustments
• -receives cortical input, provides negative feedback to cortex to modulate movement

• Striatum: putamen (MOTOR) + caudate (COGNITIVE)
• Lentiform: putamen + GP

• 1. Excitatory Pathway
• 2. Inhibitory Pathway
• 
  

• DA binds:
• -D1 (stimulating excitatory pathway)
• -D2 (inhibiting inhibitory pathway)

--> increased movement

• -cortical inputs stimulate the striatum
• -disinhibits STN via GPe
• -STN stimulates GPi/SNr which inhibit the thalamus

DECREASED MOTION

• -cortical inputs stimulate the striatum to release GABA
• -disinhibits the thalamus by GPi/SNr

INCREASED MOTION

• Precentral gyrus: primary motor cortex
• Postcentral gyrus: primary sensory cortex
• Occiptal lobe (above and below calcarine sulcus): primary visual cortex
• Transverse Temporal Gyri: primary auditory cortex
• Posterior Superior Temporal gyrus: Wernicke's Area
• Posterior Inferior Frontal gyrus: Broca's Area
• Arcuate Fasciculus: connects Wernickes and Brocas

Topographical representation of sensory and motor areas of cerebral cortex

• ACA: anteromedial surface (medial frontal lobe, superior medial parietal lobe)

MCA: lateral surface

PCA: posterior and inferior surface (medial occipital, medial and inferior temporal)

• Watershed zones:
• -ACA/MCA
• -PCA/MCA

• -tight autoregulation
• -perfusion driven primarily by CO₂

Hypoxemia increases cerebral perfusion pressure when ONLY when PO₂ < 50 mmHG

Large venous channels that run through the dura and empty into internal jugular vein

• Functions:
• 1. Drain blood from cerebral veins
• 2. Receive CSF from arachnoid granulations

Intraventricular foramina of Monroe: connect lateral and third ventricles

Cerebral Aqueduct (of Sylvius): connects third and fourth ventricle

Foramina of Luschka (Lateral): connects fourth ventricle to subarachnoid space

Faramen of Magendie (Medial): connects fourth ventricle to subarachnoid space

**CSF made by ependymal cells of choroid plexus

• 31 total (just like flavors of Baskin Robins!)
• -8 cervical
• -12 thoracic
• -5 lumbar
• -5 sacral
• -1 coccygeal

• C1-C7 exit above vertebrae
• All others exit below

In adults the spinal cord extends to L1 - L2

Subarachnoid space extends to S2

Lumbar puncture: L3-L4, L4-L5 (cauda equina)

"To keep the cord alive keep the spinal needle between L3 and L5"

• 1. Dorsal Columns
• 2. Lateral Spinothalamic Tract
• 3. Intermediate Horn Sympathetics
• 4. Anterior Spinothalamic Tract
• 5. Lateral Corticospinal Tract

Pressure, vibration, fine touch, proprioception

• First Order Neuron:
• -Sensory neuron with cell body in DRG
• -ascends ipsilaterally in dorsal column

• Synapse 1:
• -ipsilateral nucleus cuneatus or gracilis

• Second Order Neuron:
• -Decussates in medulla
• -ascends contralaterally in medial lemniscus

• Synapse 2:
• -VPL (thalamus)

• Third Order Neuron:
• -Sensory cortex

**Dorsal column organized as you are with arms outside and legs inside

• Lateral: pain, temperature
• Anterior: crude touch, pressure

• First Order Neuron:
• -sensory nerve (Adelta and C fibers) with cell body in dorsal root ganglion

• Synpase 1:
• -ipsilateral gray matter at the level it enters

• Second Order Neuron:
• -decussates at anterior white commisure
• -ascends contralaterally

• Synapse 2:
• -VPL

• Third Order Neuron:
• -Sensory Cortex

**Legs are lateral

Descending voluntary movement of contralateral limbs

• First Order Neuron:
• -UMN: cell body in primary motor cortex
• -descends ipsilaterally through internal capsule, decussates in the pyramids of the medulla, descends contralaterally

• Synapse 1:
• -cell body of anterior horn in spinal cord

• Second Order Neuron:
• -LMN: leaves spinal cord

• Synapse 2:
• -NMJ

**Legs are Lateral in Lateral corticospinal tract

C2: posterior skull cap

C3: high turtle neck shirt

C4: low collar shirt

• T4: nipple line
• "T4 at the teat pore"

T7: xiphoid process

• T10: umbilicus (early appendicitis referral)
• "T10 at the belly butten"

• L1: inguinal ligament
• "L1 is IL (Inguinal Ligament)

• L4: includes kneecaps
• "Down on ALL 4s (L4)"

• S2-S4: erection, sensation of penile and anal zones
• "S2, 3, 4 keep the penis off the floor"

• Biceps: C5 nerve root
• Triceps: C7 nerve root
• Patella: L4 nerve root
• Achilles: S1 nerve root

• "1,2 buckle my shoe; 3,4 kick the door; 5,6 pick up sticks; 7,8 shut the gate"

• -present in infant but absent in normal adult
• -disappear in 1 year
• -inhibited by mature frontal lobe
• *may reemerge in frontal lobe lesions

• Moro Reflex:
• -"hang on for life"
• -abduct/extend limbs when startled, then draw together

• Rooting Reflex:
• -move head toward side if cheek or mouth is stroked (nipple seeking)

• Sucking Reflex:
• -suckling when roof of mouth touched

• Palmar Reflex:
• -curl fingers if palm stroked

• Plantar Reflex:
• -Babinski sign
• -dorsiflex big toe, fanning of other toes

• Galant reflex:
• -stroke along one side of spine if baby is face down causes lateral flexion of lower body toward side

• Optic Chiasm
• Infundibulum
• Anterior perforated substance
• Tuber cinereum
• Mammillary body
• Cerebral peduncle (crus cerebri)
• Pons
• MCP
• Pyramid

• CNs that lie medially at brain stem: III, VI, XII:
• 3(x2) = 6(x2) = 12
• Motor = Medial

Pineal Gland: melatonin secretion, circadian rhythms

Superior Colliculi: conjugate vertical gaze center

Inferior Colliculi: auditory

"Your eyes are above your ears, and the superior colliculus (visual) is above the inferior colliculus (auditory)"

• "Oh, Oh, Oh To Touch And Feel Virgin Girls' Vaginas, Ahhhh, Heaven"
• Olfactory
• Optic
• Oculomotor
• Trochlear
• Trigemnial
• Abducens
• Facial
• Vestibulochochlear
• Glossopharyngeal
• Vagus
• Accessory
• Hypoglossal

• "Some Say Marry Money But My Brother Says Big Brains Matter Most"
• S=sensory
• M=motor
• B=both

• Foramina:
• "Cleaners Only Spray Smelly Stuff Right On Smelly Idiots In J. Jonah Jameson High"
• Cribiform plate (CNI)
• Optic canal (CNII)
• Superior orbital fissure (CNIII)
• Superior orbital fissure (CNIV)
• Superior orbital fissure (CNV V1)
• Foramen Rotundum (CNV V2)
• Foramen Ovale (CNV V3)
• Superior orbital fissure (CNVI)
• Internal Auditory meatus (CNVII)
• Internal Auditory meatus (CNVIII)
• Jugular foramen (CNIX)
• Jugular foramen (CNX)
• Jugular foramen (CNXI *enters through FM)
• Hypoglossal canal (CNXII)

Olfactory

• Function:
• -smell

• Type:
• -sensory

• Foramen:
• -cribiform plate

*only CN without thalamic relay to cortex

Optic

• Function:
• -sight

• Type:
• -Sensory

• Foramen:
• -optic canal

Occulomotor

• Function:
• -SR, IR, MR, IO
• -pupillary constriction
• -accomodation
• -levator palpebrae

• Type:
• -motor

• Foramen:
• -superior orbital fissure

Trochlear

• Function:
• -SO

• Type:
• -Motor

• Foramen:
• -superior orbital fissure

Trigeminal

• Function:
• -facial sensation (ophthalmic, maxillary, mandibular)
• -somatosensation to anterior 2/3 tongue
• -muscles of mastication

• Type:
• -Both

• Foramen: "Standing Room Only"
• -V1: superior orbital fissure
• -V2: foramen rotundum
• -V3: foramen ovale

Abducens

• Function:
• -LR

• Type:
• -Motor

• Foramen:
• -Superior Orbital Fissure

Facial

• Function:
• -Facial movement
• -chordae tympani (taste to anterior 2/3 tongue)
• -lacrimation
• -salivation (submandibular, sublingual glands)
• -obicularis oculi (eyelid closing)
• -stapedius muscle (dampens loud sounds)

• Type:
• -Both

• Foramen:
• -Internal Acoustic Meatus

**Facial nerve passes through the parotid gland but does NOT innervate it

Vestibulocochlear

• Function:
• -hearing
• -balance

• Type:
• -Sensory

• Foramen:
• -internal acoustic meatus

Glossopharyngeal

• Function:
• -taste (posterior 1/3 tongue)
• -sensation (post 1/3 tongue)
• -swallowing
• -salivation (parotid gland)
• -monitoring carotid body and sinus chemo and baroreceptors
• -stylopharyngeus (elevates pharynx)

• Type:
• -both

• Foramen:
• -Jugular foramen

Vagus

• Function:
• -taste from epiglottic region
• -swallowing
• -palate elevation
• -midline uvula
• -talking
• -coughing
• -thoracoabdominal viscera
• -monitoring aortic arch chemo and baroreceptors

• Type:
• -Both

• Foramen:
• -jugular foramen

Accessory

• Function:
• -SCM (head turning)
• -Trapezius (shoulder shrugging)

• Type:
• -Motor

• Foramen:
• -in through foramen magnum
• -out through jugular foramen

Hypoglossal

• Function:
• -tongue movement

• Type:
• -motor

• Foramen:
• -hypoglossal foramen

• -in brain stem tegmentum

• Midbrain: CNIII, CNIV
• Pons: CNV, VI, VII, VIII
• Medulla: CNIX, X, XII
• Spinal Cord: CNXI

• Lateral Nuclei = sensory (aLar plate)
• ------Sulcus Limitans--------
• Medial Nuclei = Motor (basal plate)

• Corneal:
• -Afferent = CNV1
• -Efferent = CNVII

• Lacrimation:
• -Afferent: CNV1
• -Efferent: CNVII
• **loss of reflex does not preclude emotional tears

• Jaw Jerk:
• -Afferent: V3 (muscle spindle reflex)
• -Efferent: V3 motor to masseter

• Pupillary:
• -Afferent: CNII
• -Efferent: CNIII

• Gag:
• -Afferent: CNIX
• -Efferent: CNX

• Function:
• -drains blood from eye and superficial cortex
• -drains into internal jugular vein

• Nerves:
• -CN III, IV, V1, V2, postganglionic sympathetic fibers
• **nerves that control EOM + V1/V2

• Arteries:
• -Internal Carotid

• **Cavernous Sinus Syndrome

• Close Jaw:
• -Masseter
• -teMporalis
• -Medial pterygoid
• "M's Munch"

• Open Jaw:
• -Lateral pterygoid
• "Lateral Lowers"

"It takes more muscles to keep your mouth shut"